Calculation and experimental study of the dynamic characteristics of the spacecraft telescope frame mockup

The article presents a computational and experimental study of the dynamic characteristics of a spacecraft telescope frame mock-up. The main attention is paid to the methodology of vibrodynamic tests using a three-component laser vibrometer and the creation of a finite element model of the mock-up under study. To analyze the dynamics of the structure, the main criteria such as modal parameters, model validation and harmonic analysis are defined. Particular attention is paid to the effect of experimental data transformation on the accuracy of calculating the modal reliability criterion. The telescope frame mock-up, which is a truss structure fixed on springs, is investigated. The tests were carried out by applying a random impact of the “white noise” type. The dynamic characteristics of the structure were obtained, including the natural frequency of oscillations, which was 93.7 Hz. The experimental data were compared with the results of finite element modeling, which showed a significant discrepancy between them, especially in the area of natural frequencies. This indicates the need to adjust the finite element model. Various criteria for assessing the compliance of calculated and experimental models are considered, such as the coordinate criterion of modal validity (COMAC), the criterion of modal validity (MAC), the mutual guarantee criterion (CSAC) and the mutual proportionality factor (CSF). These criteria help to assess the degree of coincidence of vibration modes and frequency characteristics. An analysis of the effect of transforming experimental data into different units of measurement on the results of calculating these criteria is carried out. It is concluded that the current calculation model requires revision and clarification of parameters to achieve better compliance with reality.